The present invention is directed to an improved orthodontic archwire, and more particularly, to a vertically-acting, and optionally horizontally-acting, archwire that provides for rapid tooth positioning and overall enhanced results in orthodontic treatment.
Orthodontic archwires are utilized to provide corrective tooth positioning forces in orthodontic treatment programs. For such purposes, archwires may be provided so as apply extrusive and/or intrusive forces to maxillary and/or mandibular bicuspids and/or incisors. Further, archwires may be employed to apply arch widening or narrowing forces.
Typically, the use of orthodontic archwires progresses in a number of phases. In a traditional first phase of treatment one or a succession of relatively flexible wires are utilized to position teeth to a first degree, followed by a second phase in which one or a succession of relatively stiff finishing archwires are employed to obtain a final desired arch form. The flexible wires utilized in phase I treatment may be generally characterized as having a relatively low modulus of elasticity in tension, including for example super elastic nickel titanium archwires, titanium molybdenum archwires and stainless steel woven, twisted or braided archwires. In contrast, phase II archwires may be generally characterized as having a relatively high modulus of elasticity in tension, including in particular monolithic stainless steel archwires arcuately configured to lie within a flat plane or to match a desired curve of spee in a passive state.
Although orthodontic archwires of the above-noted nature have been employed to yield acceptable results, the cumulative time of treatment can be quite extensive and entail a significant number of office visits. Further, depending on the type of orthodontic archwire(s) employed, undesired tooth movement may accompany intrusive/extrusive tooth movement, including in particular undesired molar tipping (e.g., crown tipping to the distal/root tipping to the mesial), molar rotation (e.g., to the distal) and molar root movement (e.g., the buccal).
In view of the foregoing, a primary objective of the present invention is to provide an orthodontic archwire that effects rapid bicuspid intrusion/extrusion and/or rapid incisor extrusion/intrusion.
An additional objective of the present invention is to address the above-noted objectives, while reducing or substantially avoiding undesired tooth movement, including undesired molar tipping, rotation and/or root movement.
Yet another objective of the present invention is to provide a multi-functional orthodontic archwire that may be utilized to achieve rapid bicuspid and/or incisor intrusion/extrusion as may be desired, while further providing for an increase or decrease of inter-canine and inter-molar distances in the maxillary and/or mandibular as may be desirable on a patient-by-patient basis.
One or more of the above-noted objectives and additional advantages may be realized in an inventive orthodontic archwire that includes a central curved portion and first and second end portions extending from opposing ends of the central curved portion. The central curved portion includes a middle section and first and second intermediate sections extending from opposing ends of the middle section. In a passive state, the middle section arcuately projects one of upwardly and downwardly with respect to a reference plane (e.g., to define a shallow, upright or downward arc), and the first and second intermediate sections arcuately project oppositely to the middle section with respect to the reference plane (e.g., to define a shallow, downward or upright arc). By way of further descriptive illustration, when the arcuate middle section is oriented upward and the arcuate intermediate sections are oriented downward, a gentle saddle-like configuration is defined by the archwire. As will be further described, the opposite vertical orientations of the arcuate middle and intermediate sections provide for the deflection of such sections into opposite corresponding orientations when the archwire is activated upon installation in a patient""s mouth. Such deflective activation provides the necessary vertically-acting, corrective positioning forces to effect bicuspid intrusion/extrusion and/or incisor extrusion/intrusion.
In one aspect of the present invention, the first and second end portions may be provided to extend substantially non-convergently (i.e., relative to each other) from opposing ends of the central curved portion of the archwire in both a passive state and when the archwire is installed. More particularly, in a passive state, the end portions may be provided to extend from opposing ends of the central curved portion within an angle range of between about 0xc2x0 to xc2x130xc2x0 relative to an archwire mid-line (e.g., in a plan view). In a preferred embodiment, the end portions each extend linearly from the central curved portion in a plan view.
In another related aspect of the present invention, the first and second end portions of the inventive archwire may be provided so as to extend from opposing ends of the central curved portion substantially parallel to or substantially within the reference plane of the archwire in both a passive state and when the archwire is installed. More particularly, the first and second end portions may extend from opposing ends of the central curved portion within an angle range of between about xc2x15xc2x0 relative to the reference plane (e.g., in a side view). In one embodiment, the end portions each extend substantially linearly within or parallel to the reference plane. As will be appreciated, the reference plane of the archwire is established so that upon installation of the archwire the reference plane will assume a position substantially parallel to a desired occlusal plane.
The provision of end portions configured in accordance with one or more of the noted aspects reduces or substantially avoids the application of undesired forces to interconnected teeth during use of the inventive archwire. As such, undesired tooth movement is reduced or avoided, including, for example, undesired molar tipping, rotation and/or root movement.
In another aspect of the present invention, the arcuate middle section of the orthodontic archwire may be provided so as to have a maximum projection of between about 0.3 mm and 0.6 mm relative to the reference plane in a passive state. Further, the arcuate first and second intermediate sections may be provided to each have a maximum projection of between about 2 mm and 4 mm relative to the reference plane in a passive state.
In a related important aspect of the present invention, the archwire may be provided to have a modulus of elasticity in tension, sometimes referred to as a modulus of stiffness, of between about 2.8xc3x97106 and 3.2xc3x97106. In a different measure, the archwire may be provided to have an ultimate tensile strength of between about 275 KSI and 330 KSI (i.e., thousand pounds per square inch), and most preferably at least about 310 KSI. Further, the archwire preferably has a round cross-section, with a diameter of between about 0.012xe2x80x3 and 0.022xe2x80x3. Square, rectangular, woven and braided configurations may also be utilized. By way of example, the archwire may be fabricated from relatively hard, high tensile metal and/or metal alloy comprising chromium, nickel, molybdenum, manganese or iron.
In a further related aspect of the invention, the inventive archwire may be provided so that upon deflected activation when installed the arcuate middle section applies a total force of between about 45 gm to 65 gm per mm of deflection to the interconnected teeth (e.g., 135 gms-195 gms applied for a 3 mm deflection). Similarly, the intermediate sections may be provided so that upon activation they each apply a total force of between about 45 gm to 65 gm per mm deflection to the interconnected teeth.
In an additional aspect of the present invention, a plurality of archwires having one or more of the above-noted features may be provided in varying cross-widths for intended use in the maxillary and/or a plurality of archwires having one or more of the above-noted features may be provided in varying cross-widths for intended mandibular use. The provision of such archwire sets allows for the successive multi-functional use of the archwires to achieve tooth extrusion/intrusion contemporaneous with a desired degree of arch expansion, narrowing or width-maintenance.
In yet an additional aspect of the present invention, the curved portion of the inventive orthodontic archwire may optionally include first and second anterior step-out portions interposed between the arcuate middle section and the arcuate first and second intermediate sections, respectively. The provision of the anterior step-out portions accommodates the buccal offset projection of the cuspids in normal applications.
In a related important aspect of the present invention, the archwire may be provided to have a relatively high modulus of elasticity in tension, sometimes referred to as a modulus of stiffniess. In one measure, the archwire may be provided to have an ultimate tensile strength of between about 275 KSI and 330 KSI (i.e. thousand pounds per square inch), and most preferably at least about 310 KSI. Further, the archwire preferably has a round cross-section, with a diameter of between about 0.012xe2x80x3 and 0.022xe2x80x3. Square, rectangular, woven and braided configurations may also be utilized. By way of example, the archwire may be fabricated from relatively hard, high tensile metal or metal alloy comprising chromium, cobalt, nickel, molybdenum, manganese or iron (e.g. a chromium-cobalt alloy).
In conjunction with the present invention an inventive method is also disclosed for use of one or more inventive orthodontic archwires. Such inventive method includes the step of first installing a first orthodontic archwire in a patient""s mouth, wherein the first orthodontic archwire is deflected from a passive state to an activated state, and wherein the first orthodontic archwire is of a configuration having one or more features as described above. Specifically, the first orthodontic archwire may include first and second end portions extending from opposing ends of a central curved portion, said central curved portion having oppositely oriented middle and first/second intermediate sections which arcuately project from the reference place, and wherein the archwire preferably has an ultimate tensile strength of at least about 310 KSI. The first installing step of the inventive method may include the step of interconnecting the first and second end portions of the first orthodontic archwire to appliances on opposing upper or lower molars in said patient""s mouth, wherein upon said activation the first and second end portions of the orthodontic archwire extend from the appliances in one of a substantially parallel orientation and substantially coplanar orientation relative to the reference plane. Further, upon installation the first and second end portions of the orthodontic archwire may preferably extend in a substantially nonconvergent manner relative to said curved central portion.
Following the first installing step, the method may further comprise the step of first removing the first orthodontic archwire from thee patient""s mouth, preferably when the middle and intermediate sections of the first orthodontic archwire have reached a position coincidental with the reference plane, then utilizing an orthodontic finishing wire (e.g. stainless steel). For purposes hereof, the term xe2x80x9corthodontic finishing wirexe2x80x9d is utilized to mean a monolithic finishing wire which substantially lies within a flat plane or substantially follows a continuous predetermined curve of spee in a passive state.
As will be appreciated upon further description, a two phase treatment method as described above provides for rapid and effective tooth repositioning. In this regard, the use of relatively stiff archwires in each of the two phases particularly differentiates the inventive method from prior art techniques.
By way of elaboration, the first installing step of the inventive method may comprise the steps of deflecting the middle section of the first orthodontic archwire into an arcuate orientation opposite to and even more extreme than its orientation in a passive state, and interconnecting the deflected middle section to at least one incisor in the patient""s mouth (e.g., via ligation to a orthodontic appliance mounted on the tooth). Similarly, the first installing step may also include the steps of deflecting the intermediate sections of the first orthodontic archwire into arcuate orientations opposite to and even more extreme than their orientations in a passive state, and interconnecting each of the deflected intermediate sections to at least one bicuspid in the patient""s mouth (e.g., via ligation appliances mounted to each of the teeth). As will be appreciated, such deflection and interconnection serves to apply the desired extrusive/intrusive forces to achieve corrective tooth positioning. More particularly, the first orthodontic archwire may be provided so that upon activation the middle section applies a total force of between about 45 gm to 65 gm per mm deflection to the interconnected incisor(s). Similarly, the intermediate sections may be provided so that upon activation they each apply a total force of between about 45 gm and 65 gm per mm deflection to the interconnected bicuspid(s).
In another aspect, the inventive method may further comprise the use of a plurality of inventive orthodontic archwires having one or more features described above during phase I treatment. For example, a first inventive orthodontic archwire may be utilized which applies extrusive/intrusive tooth positioning forces and one of an expansive and narrowing force upon installation in a patient""s mouth. Then, after removal of the first orthodontic archwire, a second inventive orthodontic archwire may be installed/removed prior to the finishing wire utilization step. The second archwire may provide for continued vertical tooth positioning and maintenance of a desired arch width prior to the use of an orthodontic finishing wire(s). In this case, it is preferable to remove the second orthodontic archwire when the middle and intermediate sections have reached a partially deflected state coincidental with the reference plane.
Numerous additional aspects, applications and advantages of the present invention will be apparent to these skilled in the art upon consideration of the further description that follows.